Omar S. Thornton is seen in this photo posted on Facebook. Omar S. Thornton opened fire early Tuesday morning during a shift change at Hartford Distributors, a beer distributorship near Hartford, Connecticut. ABC News has been told that nine people, including the gunman, have died.

Thornton opened fire right after meeting with the 50-year-old Hollander, who had given him a choice either to be fired or quit. Thornton had been trailed by a private investigator hired by the company after he was suspected of stealing alcohol from the distributor, police said at a news conference today.

In the 911 call, Hollander described a scene of complete chaos.

"There are people running all over the place," he said. "He's running, he's shooting at someone else, he's still shooting. He's still running after people, he's not leaving."

When the 911 operator asks Hollander if the gunman had worked at the distributor, Hollander said, "Yeah, 'til I just fired him."

"Today, just now, before he started shooting," said Hollander. "He's chasing people in the parking lot."

Thornton passed over several people during the rampage inside and around the distributor, according to Manchester Police Lt. Chris Davis, who said authorities believe the first few victims were likely targeted.

Davis declined to specify who the first of Thornton's victims were, but said that many of those who were killed were "executives" or "higher level" employees. All of those who were shot were 49 or older.

The first of Thornton's victims were found right outside the kitchenette where authorities believe he had stowed two handguns in a red metal lunchbox.

At one point, Thornton chased two people outside of the building and shot them, said Davis. He shot through a glass window to reenter the building, which was locked, and continued shooting.

The first 911 call was received just before 7:30 a.m., according to Davis.

When authorities arrived just three minutes later, the scene was "chaotic" and the walls of the massive distributorship were hard to navigate because of the stacks of liquor cartons that created makeshift hallways.

"We got calls from people under their desks and hiding in their offices," said Davis. "He really went through the whole building in a fairly short amount of time."

One of the 911 calls was made by an unidentified woman who was crying as she told the operator what Thornton looked like.

"He's a tall black guy he's like the only lack guy who works here almost," the woman told the operator. "Come get me."

Another unidentified man called 911 and told operators that he knew people were dead.

"I know for a fact two people are dead in here. In the hallway, they were both shot right in the head," the man said.

Thornton had signed a one-line resignation letter after he was confronted with video surveillance evidence that showed him stealing alcohol from the distributor. A moment later, Thornton requested a drink of water and went to a nearby kitchenette where Davis said he had stowed his weapon-packed lunchbox.

Thornton used two 9mm handguns during the attack, and authorities later found another shotgun and extra clip of ammunition in his car. Davis said that it is believed the three guns were purchased at an East Windsor gun store. Hoffman's Gun Center, a store in East Windsor, is listed on Thornton's Facebook page.

Wilbert Holliday, Thornton's uncle, told ABC News that he didn't think the shooting was random and that his nephew had complained about racial discrimination at work.

Holliday said that Thornton called his mother after the shooting spree and talked to her for about ten minutes, telling her, "I killed the racists that were bothering me."

According to Holliday, Thornton had filed complaints with the Teamsters union about alleged racial harassment and had pictures on his cell phone of the N-word and a hangman's noose scrawled on a bathroom wall at Hartford Distributors.

Union representatives strongly denied the allegations.

Gregg Adler, a union attorney, said Thornton had never filed a harassment complaint with the union, but had filed a separate grievance that had been settled in his favor regarding insufficient training. Adler said that it was clear Thornton knew the protocol for filing a complaint.

Asked about the union's denials that Thornton had filed a complaint, Holliday said, "Of course they're going to say that."

The newest employee of the distributorship's 65 drivers, Thornton began shooting at what would have been one of the busiest times of day at the warehouse.

"It couldn't have been a worse time of day," said John Hollis of the Teamsters Union. "The day shift was coming in and the office staff was all there. It was the time of day where the most employees would be in the building."